Adding a delay in my code, not working. C++ - windows

Question

Trying to make simon says game as my semester project, problem is I cant add a delay between the colors when they change,
i.e i want to add a delay so that when one box color changes, then after about 3~4 seconds the next box color changes, but the problem is when I put the Sleep() in my for loop, the system pauses for the amount given as a whole, then displays all the colors changed at the same time not one by one....
Any help, here is the function that i call when the game's start button is clicked. How to fix it ?
void flash()
{
srand(time(NULL));
int x;
for (int i = 5; i > 0;i--)
{
x = rand() % 4;
if (x == 0)
{
button1->BackColor = System::Drawing::Color::Blue;
}
else if (x == 1)
{
button2->BackColor = System::Drawing::Color::Blue;
}
else if (x == 2)
{
button3->BackColor = System::Drawing::Color::Blue;
}
else if (x == 3)
{
button4->BackColor = System::Drawing::Color::Blue;
}
Sleep(500);
}
}
P.s I have tried to put the sleep in the if statements but that doesn't work either, Any help please ?

Answer 1

As your code is single-treaded and you are updating the colors of the buttons in a loop, there is (currently) no chance for the application's standard drawing routines to kick in, until the loop is finished. If you do want a redraw while being in the loop, you have to manually issue it by (e.g.):
button1->Invalidate();
button1->Update();
Please be aware that, if you stay in the loop for too long, windows does recognize that your application is not responding to windows messages and renders it "unresponsive" (window fading to half white). To circumvent this, you can use the Timer class from System::Windows::Forms to implement the delay behaviour.